Season both sides of the walleye with salt and freshly ground black pepper. Coat both sides of the walleye fillet with flour, tapping off the excess. Heat the butter in a medium nonstick skillet over medium-high heat and cook the walleye on one side for 2 to 3 minutes, or until golden. Turn the fillet over and cook until fish is opaque and cooked through. Remove to a plate and keep warm. Add the sliced mushrooms and diced tomatoes to the fish pan and cook until mushrooms are golden and any liquid has evaporated. Add some of the garlic wine sauce and season with salt and pepper, to taste. Serve the fish over linguini and top with the pan sauce. Garnish with a lemon wedge.
Melt the butter in a medium saucepot over medium heat. Add the garlic and saute until beginning to brown, about 5 minutes. Add the water, clam base, white wine, and lemon pepper, and simmer until reduced and thickened, about 10 minutes.